PT-1738 - add mongos to pt-mongodb-summary

[BON4]

This commit adds mongos instances report table to the mongodb summary

Modified summary will look like this:

# Mongos #################################################################################################
Host                              LastPing                     Version         Uptime (sec)
my-cluster-name-mongos-0:27017    2026-02-16T13:01:22Z         8.0.17-6        3553           
my-cluster-name-mongos-1:27017    2026-02-16T13:01:26Z         8.0.17-6        3543           
my-cluster-name-mongos-2:27017    2026-02-16T13:01:28Z         8.0.17-6        3533           

# Instances 
...

• The contributed code is licensed under GPL v2.0
• Contributor Licence Agreement (CLA) is signed
• util/update-modules has been ran
• Documentation updated
• Test suite update

[svetasmirnova]

We need a test case for thsi feature.